Xamarin/Maui Android, Task.Delay().ContinueWith, DisplayAlert not fired

August 2, 2022

I have this code, but Display alert never fired, can’t understand – why so?

await Task.Delay(_doublePressTimeout - _buttonReleaseTimeout)
    .ContinueWith(async c =>
    {
        if (pushed != Constants.Direction.Empty)
        {
            await Shell.Current.DisplayAlert("qwe", pushed.ToString(), "OK");
        }
    });

But works this way:

await Task.Delay(_doublePressTimeout - _buttonReleaseTimeout);
if (pushed != Constants.Direction.Empty)
{
    await Shell.Current.DisplayAlert("qwe", pushed.ToString() + " begin", "OK");
}

WHY?

>Solution :

Tasks have an implicit .ConfigureAwait(true) when they’re awaited straight up, which is why you have a warning to state it explicitly (or even better, use .ConfigureAwait(false) selectively for large performance increases where applicable).

.ContinueWith can also capture the context and/or schedule the continuation on specific threads, which you should be doing for UI access, but you need to call the overload with the parameters for it.

That said, you’ll be hard pressed to find a valid use case for .ContinueWith over just task awaiting. As you can see from your own example, it’s easy to translate broken .ContinueWith to correct (and simpler) await Task code.